When Diesel fuels and Otto fuels, that are made up of a mixture of hydrocarbons are combusted, some hydrocarbons still remain in the exhaust gas, even after the combustion. To reduce the emission, upper boundaries are fixed, which limit the emission of volatile hydrocarbons.
GARB legislation (GARB: California Air Resources Board), for instance, requires the monitoring of controller functions of the fuel system. One requirement in this connection is the diagnosis of the time to achieving readiness for operation (TTCL: time-to closed loop). Alternatively, it is possible to monitor individually all activating conditions for the controller function, so that an indirect diagnosis comes about for achieving readiness for operation of the regulation.
The condition of saturation temperature is calculated in the engine control based on numerous input variables, the purpose being to hit as exactly as possible the point in time of achieving the condition of saturation temperature, and thereby to bring about the readiness for operation of the exhaust gas sensor. This is required particularly in the case of heated exhaust gas sensors which are sensitive to droplets and spray water. In this context, input variables are used which have not been sufficiently diagnosed within the meaning of the legislation.